A breast pump system comprises a breast pump acting as an expression unit, and an operating unit to operate the breast pump. The expression unit has a funnel which receives the breast and a receptacle in which the expressed milk is collected. The operating unit comprises a vacuum pump driven by a motor. In use, the vacuum pump applies a vacuum to the breast which enables milk to be expressed. The vacuum is applied to the breast either directly or via a membrane located in the expression unit which deforms and so causes a vacuum to be generated in the funnel.
Breast pump systems are typically configured to be assembled and disassembled so that any part of the breast pump system that has been in contact with breast milk can be sterilised after each use and so that the breast pump system can be stored in a convenient place when it is not being used. However, when storing a breast pump system in a disassembled state, there is a risk of damaging or losing parts of the breast pump system.